Eating beef could threaten sons' fertility

Roger Highfield, Science Editor, "Eating beef could threaten sons'
fertility", Telegraph, March 28, 2007,
Link: http://www.telegraph.co.uk/global/ma...28/nbeef28.xml

The sons of women who regularly ate beef during pregnancy are more
likely to have low sperm counts, according to a report published
today.

Copenhagen University researchers concluded that sperm counts were
falling in the West more than a decade ago and exposure to pesticides
and industrial chemicals have long been under suspicion, with
principle suspects including "gender- bender" chemicals that act like
the human sex hormones.

Today, an American team concludes that women who ate a lot of beef
while pregnant had sons who were more likely to suffer from poor sperm
quality and suggest that the growth promoters used in cattle may be
responsible.

The study of men living in the USA and born between 1949 and 1983
revealed that those whose mothers ate more than seven beef meals a
week had a sperm concentration that was more than 24 per cent lower
than in men whose mothers ate less beef.

In addition, three times more sons of high beef consumers had a sperm
concentration that would be classified as sub-fertile by World Health
Organization standards, in comparison to men whose mothers ate less
beef.

One British expert said that the findings are "alarming." Another
added: "Don't mess with growth promoters is the obvious take home
message."

But others were sceptical about findings which were based on asking
women how often they ate beef decades ago.

Prof Shanna Swan, lead author of the study published in the journal
Human Reproduction, said: "These findings suggest that maternal beef
consumption is associated with lower sperm concentration and possible
sub-fertility, associations that may be related to the presence of
anabolic steroids and other xenobiotics (foreign chemicals) in beef.

"Theoretically, the foetus and young children are particularly
sensitive to exposure to sex steroids. Therefore, the consumption of
residues of steroids in meat by pregnant women and young children is
of particular concern."

But while the study results revealed a significant link between the
lowest sperm counts and mothers who were the highest beef consumers,
researchers could not pinpoint hormones, pesticides or other
environmental chemicals as a direct cause.

"What we're really doing here is raising an issue," said Prof Swan,
who is director of the Centre for Reproductive Epidemiology at the
University of Rochester, New York.

"The average sperm concentration of the men in our study went down as
their mothers' beef intake went up."

Prof Swan and her colleagues recruited couples to the study when the
pregnant women attended prenatal clinics between 1999 and 2005. As
well as asking questions about the couples themselves (medical
histories, lifestyle factors such as smoking, alcohol consumption and
diet), the researchers requested the men to ask their mothers to fill
in a brief questionnaire about their diet while pregnant with their
sons.

The men also provided semen samples. Out of 773 men who provided
samples, information was available for 387 on how many beef meals
their mothers ate during their pregnancies.

Prof Swan said: "The number of beef meals consumed by the mother was
significantly and inversely related to her son's sperm concentration.
Sons of high beef consumers had an average sperm concentration of 43.1
million sperm per millimetre of seminal fluid, while sons of mothers
who ate less beef had an average of 56.9 million sperm - a
statistically significant difference of 24.3 per cent.

"Among sons of mothers whose beef consumption was not high, only 5.7
per cent had sperm concentration below the WHO threshold for sub-
fertility of 20 million sperm per millimetre of seminal fluid. This
was significantly less than the 17.7 per cent of men whose mothers
were high beef consumers who fell below this threshold.

"The proportion of men with sub-fertile sperm concentration and of men
with a history of possible sub-fertility increased the more beef meals
the mothers had eaten while pregnant. These findings suggest that
maternal beef consumption is associated with lower sperm concentration
and possible sub-fertility.

"However, I must point out that most mothers in this study lived in
North America and our findings may not apply to other regions. In
addition, pesticides, other contaminants and lifestyle factors
correlating with greater beef consumption may play a role in the
effect we observed.

"In order to clarify whether prenatal exposure to anabolic steroids is
responsible for our findings, this study needs to be repeated in men
born in Europe after 1988 when growth promoters were no longer
permitted in beef sold or produced there." The study was not devised
for making recommendations, she added.

"However, if a pregnant woman is concerned and wants to take
precautionary action, there are a few things she can do that may lower
risk and probably are not harmful. She might restrict her consumption
to organic beef. She can also reduce the amount of beef she consumes
while pregnant, if she is careful to eat sufficient protein from other
sources."

Dr Allan Pacey at The University of Sheffield, said: "That hormones
given to cattle might have lowered the sperm counts of adult men
because their mothers ate a lot of beef when they were pregnant with
them, is alarming to say the least. This clearly needs to be
investigated further."

Prof Richard Sharpe of the Medical Research Council's Human
Reproductive Sciences Unit, Edinburgh, said: "This is a serious
scientific study conducted in the most rigorous fashion, so it needs
to be taken seriously.

"The difficulty in repeating the study in Europe with men whose mums
conceived them after the ban on use of growth promoters in animals is
that we know that such young men have remarkably low sperm counts
overall, probably unrelated to meat consumption by their mothers, so
this may not prove possible to do.

"Also we should be looking at a similar study in relation to chicken
consumption years ago as DES was used very widely for growth promotion
in chickens whereas various growth promoters were used in cattle.
Don't mess with growth promoters is the obvious take home message."

But others were sceptical. Alastair Hay, Professor of Environmental
Toxicology, University of Leeds, said: "There are major difficulties
with this type of study not the least of which is asking a woman how
often she ate beef whilst pregnant 25-30 years ago. We have no idea
how much beef she ate which would be important to know. At the very
least this study should prompt further investigations."